Method for forming a protective pipe cap

ABSTRACT

System for protecting machine parts, such as threads, from physical and chemical damage. The parts to be protected are cleaned, coated with a separating agent, and a mold is placed around them. A protective material is inserted in the interspace between the mold and pipe end. The protective material forms a tough, protective jacket. If desired, the jacket can later be removed by means of a tear-open element or integrated weak spots. For the protection of pipe interiors, plastic material can be pressed into the end of the pipe such that it seals against the inside lining of the pipe.

BACKGROUND OF THE INVENTION

The present invention relates generally to a system for protectingthreads. More particularly, the invention relates to a system forprotecting machine threads as well as methods for producing andattaching such protective devices to machine threads.

Threads are found, for example, on machine parts and pipes. Threadstypically represent delicate areas that must be protected againstharmful mechanical and chemical effects during their transportation andstorage.

Consequently, it often becomes necessary to protect machine parts andpipes from damage by using protective caps and the like. When pipes aretransported, for example, they are often subjected to very roughtreatment. If pipes are to be used in a drilling operation, they areoften first pulled up a drilling tower and, as a result, suffer damage.The actual threads, as well as the sealing flanges on the ends of thethreads, are often damaged. Even a slightly damaged thread can render anexpensive pipe unusable.

In addition to mechanical damage to pipes, the effect of the environmentalso can render pipes unusable. Salt water, sand, dust, as well as snow,rain, and wind have adverse effects on pipes. Corroded or rusted threadsand sealing flanges render pipes unusable; repair of such chemicallydamaged pipes is expensive. Thus, it is imperative that threads andsealing flanges remain in good condition if the threads are to maintaingood connections.

In conventional practice, threads have been protected by screwingprotective caps onto them. Such caps may be either open sleeves orclosed plugs. Protective caps may be screwed onto the pipes havingthreads on their outer surface (pivots). Similarly, protective caps maybe used which have threads on their exterior surface which are screwedonto the inside threads (bushings) of a pipe.

Protection against chemical influences may be achieved by coating thethreads with grease. In addition, there are now protective caps made ofsynthetic material; such caps often provide sufficient protection forthreads.

There are many cases, however, where very high demands are made on themechanical strength of a protective cap. For example, it is common topull pipes, which are to be used in an oil drilling operation, into adrilling tower. During such an operation, the lower end of the pipeexperiences considerable mechanical stress as a result of the fact thatthe end of the pipe is dragged on the ground.

Oil drilling operations require that once the pipe is moved intoposition, the device for protecting the threads must be removed in avery short time. For the steel protective caps now often used, removalis performed by unscrewing the cap. However, this process is timeconsuming.

In order to reduce the time that is necessary to remove such a steelprotective cap, it is frequently loosened before the pipe is pulled ontothe drilling tower. Such loosening, however, often causes the protectivecap to become cross-threaded such that the thread is damaged by furtherforced loosening.

Other types of caps are available which are used especially fortransporting a pipe onto a drilling tower. Such caps, however, have thedisadvantage that they do not sufficiently protect the threads fromdirt. Also, such caps often wear out quickly. Moreover, the installationof such a special cap requires time and consequently increases the laborcosts of the drilling operation.

Use of steel caps is often undesirable, since they do not protectthreads against stronger impacts. Rather, such impacts destroy both thecap and pipe. Furthermore, steel caps often become cross-threaded, andturning the cap then leads to the destruction of the thread. Moreover,steel caps cannot protect threads against the effects of water,moisture, sand, and dust. When pipes are stored for extended periods inthe open, the threads thus are exposed to corrosion.

To avoid these disadvantages, pipe users occassionally use protectivecaps made of metal which are lined with an elastomeric material. Theelastomeric material thus provides a better seal between the steel capand the thread, as well as providing a cushion between the cap and thethread. This helps to protect against the effects of moisture as well asmechanical impact.

It is clear, however, that manufacturing protective caps with an insidelining of elastomeric material requires increased technical expertise aswell as added expense. Moreover, such lined caps are ineffective tofully protect threads against moisture, water, and dust.

A type of protective cap currently available is made of syntheticmaterial. Such synthetic caps may be produced with threads; after suchcaps have been placed on the threads of pipes, they may only be removedby the time-consuming process of unscrewing them. Some synthetic caps donot have threads; this type of construction is also undesirable, sincesuch caps do not fit tightly on the pipes. Thus, the caps are subject tobeing pulled off inadvertently and do not provide good protectionagainst the penetration of water and dirt.

In order to protect the outer and inner threads of pipes, protectivecaps, consisting of steel, plastic, or a combination of the materials,are often used. Even if such protective caps are screwed onto thethreads and do provide some protection for the threads against damage,such devices provide no protection for the inside of a pipe. As aresult, foreign substances, such as water, dirt, ice, and sand, becomelodged in the interior of the pipe.

Pipes are often inserted into wells having depths as great as severalthousand meters. Thus, a large number of pipes must be screwed together.The threads of the upper pipes must absorb the weight of the entire pipeline. Moreover, the screw connections between the pipes must often begas-tight. Therefore, complicated thread designs are frequently used. Itis clear that such threads must remain intact after their manufacture.

Pipes are also often connected by welding them together. The ends ofsuch pipes are often provided with precise welding chamfers which, likethe pipe threads, must be protected.

Pipes used in drilling operations frequently are transported or storedfor extended periods. During such times, the pipes are exposed toweather and dirt. If left without protection, the pipe ends are incontact with foreign substances and often corrode, causing a lesseningof the integrity of the pipe ends. When such pipes are then to be used,it is a time consuming and expensive task to sort out which pipes areusable.

SUMMARY OF THE INVENTION

In a principal aspect, the present invention is a method for protectingmachine or pipe threads. The thread is first cleaned and then coatedwith a separating agent that will prevent the thread from adhering to aprotective material. Next, a mold is loosely mounted around the thread.The mold and thread bear a spaced relationship to each other and thusprovide an interspace between them. Finally, the interspace is filledwith a protective material such as an elastomer.

In another primary aspect of the invention, a tear-open element isarranged in the interspace before it is filled with the protectivematerial. Thus, after the mold is removed, the protective material maybe quickly removed by pulling on the tear-open element.

In yet another primary aspect of the invention, a device for protectingthreads is provided which includes a cap of molded, protective material.The cap also includes a tear-open element for easily removing the capfrom the thread.

Thus, the present invention helps solve the problem of protectingdevices which are to be connected with each other. The invention alsoprotects the insides of such parts, such as pipe interiors. Suchprotection is most useful immediately after such devices have beenmanufactured. However, the method may be used independently of themanufacturing process. In addition, once the devices are to be used, theprotective devices can be removed with little effort and in an extremelyshort time. The invention hermetically seals the devices against suchelements as weather, dust, sand, and salt water.

A protective material may be in the mold as it is placed around thethreads or it may be injected into the interspace after the mold hasalready been attached to the pipe. The protective material may haveelastomeric properties. Polyurethane is particularly useful with thepresent invention.

By using a casted cap, the threads and sealing flanges are properlysealed; rain water, snow, ice, dust, and particularly salt water andhumid air cannot penetrate the cap and cause corrosion. Thus, the timeconsuming task of cleaning and greasing the pipe ends so that they maybe connected is eliminated. Moreover, the physical strength of the cap,particularly if the mold is left on with the casted protective material,provides protection against damage from impact.

The protective device can be made simply. Moreover, it may be quicklydetached from the protected objects. This feature is particularlyadvantageous if it is undesirable to spend time unscrewing a protectivecap in the conventional manner.

For instance, the protective caps used on pipes in earth drillingprojects must be removed very fast. Labor costs in such projects arehigh and the unscrewing of conventional protective caps for a largenumber of pipes causes considerable expense. In order to avoid thesedisadvantages, the present invention allows quick separation of theprotective cap from the pipe.

The protective device also may include a tearing lug, a tearing thread,or, generally, a predetermined breaking line so that the cap may bereadily removed. The method has the additional advantage that it may beused everywhere; it is not limited to use at the factory thatmanufactures the pipe.

The protective cap includes weak spots, cutting surfaces, or other meanswhich make it possible to remove the protective cap by tearing it. Theprotective cap may be made in a separate mold or be put onto the threadsdirectly by extruding.

It is thus the object of the present invention to produce a coveringthat may be removed with little effort and within a very short time. Inyet another primary aspect of the present invention, a stopper is madeof elastic material and can be pressed into the pipe. The outside of thestopper bears against the inside surface of the pipe, hermeticallysealing it.

For the protection of outside threads, the stopper can be made in theform of a cylinder with a closure on one end. The outer jacket of thecylinder has flexible sealing lips surrounding its periphery.

A stopper can also be made by pressing it directly into the pipe end. Inone form of the present invention which protects inside threads, thestopper is disk-shaped and includes a projection which surrounds theperiphery of the stopper. The stopper is preferably somewhat conical inshape, pointing inward toward the rest of the pipe. In addition, a wideend of the stopper pointing out of the pipe can be provided with aconical projection which surrounds the entire periphery of the pipe.

It is an object of the present invention to provide a hermetical sealingagainst the interiors of pipes and of other cylindrical housings. Thesealing lips on the preferred form of the closing stopper are usablewith pipes having different inside diameters. Thus, the production ofsuch stoppers may be limited to a few sizes, each size having theability to protect many different size diameter pipes. The outer edge ofthe stopper provides sufficient sealing for the front side of the pipe.

The disk-like stopper, which protects the insides of pipes and othersuch devices, has a shoulder which extends beyond the end of a protectorsleeve made of steel. The conical narrowing of this shoulder facilitatesthe mounting of the stopper inside the pipe. The conical wideningprovided on the disk-shaped stopper assures that the stopper willproperly seal the inside of the pipe.

The stoppers can be mounted easily because they can be pushed in by handinto the end of a pipe or into the sleeve of a protective device. As aresult, the stoppers are protected against displacement. Unlikeconventional protectors, this keeps the present stoppers from being lostwhile the pipes are being transported over great distances. Yet anotherobject of the present invention is to provide a simple, yet highlyreliable, system for sealing the interiors of cylindrical pipes orhousings.

BRIEF DESCRIPTION OF THE THE DRAWING

A preferred embodiment of the present invention is described herein withreference to the drawing wherein:

FIG. 1 is a side view of a preferred embodiment of the present inventionshowing a pipe end with threads in a casting mold;

FIG. 2 is a side view of the preferred embodiment of FIG. 1 showing thecasting mold in use and the interspace filled;

FIG. 3 is a side view of a variation of the preferred form of thepresent invention shown in FIG. 1 showing a shaft with an inside threadand a mold core;

FIG. 4 is a side view of the shaft shown in FIG. 3 with the interspacefilled;

FIG. 4a is a side view of a variation of the preferred form of theinvention shown in FIG. 1 with a mold core and a pipe end with insidethreads;

FIG. 5 is a cross-sectional view of the protective cap shown in FIG. 1with different types of weakened areas shown;

FIG. 6 is a graphical illustration of the protective cap shown in FIG. 5with an inserted tearing line;

FIG. 7 is a graphical illustration of a narrow cross-sectional area thatmay be used with the protective cap shown in FIG. 1;

FIG. 8 is a graphical illustration of the protective cap shown in FIG. 1with markings showing the course of a tearing line;

FIG. 9 is a perspective view of a variation of the preferred form of theembodiment of FIG. 1 with a common type of thread covering for a sleeve;

FIG. 10 is a perspective view of the thread covering shown in FIG. 9with four weak spots arranged on its periphery;

FIG. 11 is a perspective view of a preferred form of the presentinvention showing a covering for the threads in a closed type ofprotective cap;

FIG. 12 is a cross-sectional view of a weak spot shown in FIG. 10;

FIG. 13 is a cross-sectional view of a variation of a weak spot shown inFIG. 12;

FIG. 14 is a cross-sectional view of a variation of a weak spot shown inFIG. 12;

FIG. 15 is a cross-sectional view of a variation of the preferred formof the present invention shown in FIG. 1 with the protective devicehaving an inserted wire;

FIG. 16 is cross-sectional view of a sleeve showing a preferred form ofthe present invention;

FIG. 17 is a side view of a pipe end having a protective cap screwed on;

FIG. 18 is a side view of a closing stopper;

FIG. 19 is a cross-sectional view of a pipe end with a protective capscrewed on and a closing stopper inserted;

FIG. 20 is a cross-sectional view of a pipe end showing a closingstopper inserted and wherein the outer end of the stopper surrounds thecollar-like pipe ends and welding chamfer;

FIG. 21 is a cross-sectional view of a pipe end having an outer threadwhich is protected by a closing stopper with a collar-like formation atits outer end;

FIG. 22 is a cross-sectional view of a pipe end having an inside thread,a device for protecting threads screwed on, and a closing stopperinserted; and

FIG. 23 is a side view of an individual stopper.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, a pipe 1 has an end thread 2 which is to beprotected against corrosion and mechanical damage. A mold 3, which canbe slid over the thread 2, provides the protection. In the upper zone,the mold 3 is equipped with a filling projection 4; this fillingprojection allows material to be inserted and form the protectivedevice.

FIG. 2 shows the use of the mold 3. The material is applied in thedirection of the arrow 6 into the space formed between the thread andthe inside surface of the mold 3. After a short hardening time, theresulting device 5 hermetically seals the thread 2 and protects it frommechanical damage. As illustrated in FIGS. 1 and 2, the connecting endpiece of the thread of pipe 1 serves, as a practical matter, as the moldcore during the formation of the protective device.

According to FIG. 3, an end piece 8 rests on a shaft 7. The shaft 7,which can be replaced by pipe, includes a hollow space 9 and an insidethread 10. The mold 11, which acts as a core in this example, slidesinto the hollow space 9. Thus, as shown in FIG. 4, the interspacebetween the mold 11 and the shaft 7 can be filled through the fillingopening 11a with the material forming the protective device 12.

According to another example of the preferred embodiment shown in FIG.4a, the end of the pipe 1 has an inner thread 21 provided with aprotective covering 24. The mold 22 is made with a ring-shapedthickening 23 that seals against the pipe 1. The material insertedthrough the openings 22a thus cannot pass beyond thickening 23 and intothe interior of the pipe.

FIG. 5 shows a sleevelike protective device 5 with several different,weakened cross-sectional areas. According to one aspect of the preferredembodiment, a simple weakened cross-sectional area 13 exists on theprotective device 5. Because of its slight thickness, the protectivedevice can be opened with a simple, common cutting tool.

The insertion of a tearing wire 14 allows the protective device 5 to beopened without any other tools. According to FIG. 6, the end of the wire14 is equipped with a ring 15 for a better grip. A double-side weakening16 can also be provided in the protective device 5 if a correspondingcore is put in.

FIG. 7 shows another aspect of the preferred embodiment that uses atearing lug 17. By pulling the tearing lug 17, the protective device canalso be opened without the help of outside tools.

The example according to FIG. 8 shows the straight course of thetear-off line 18 and inserted tearing wire 14'. Another possibility forenabling the protective device to be quickly torn open is shown by aspiral arrangement of a tearing line within a weakening of thecross-sectional area 13 which can be formed by the mold.

From the illustration according to FIG. 8, it can be seen clearly thatwhen making the protective device by casting it, thread turns are formedon the protective device. Such thread turns are a mirror image, ornegative, of the turns actually found on the pipe.

By means of the example shown, it can be recognized easily that, ifsufficient time for the unscrewing of the connecting device is notavailable, it is possible to remove the protective device by a tearingelement along a defined line. Thus, considerable expense may be saved.

For the production of the protective device, the hollow, or outer, endof the parts to be protected (thread turns and seals) are cleaned andcoated with a separating agent. The mold may consist of two parts whichare connected to each other by a hinge. Alternatively, the mold may bemade of one part which can be put around the end to be protected or beslid into the hollow space to be protected.

The mold can also be provided with a separating agent in order to easethe removal of the mold after it has been filled with the elastomericmaterial. The material forming the device, such as, for example,elastomeric material, is subsequently put into the interspace betweenthe mold and the part to be protected. The filling can effectively takeplace without applying pressure to the material. The mold filling stepcan also form a tear lug 17.

After a period of about five minutes, the material will have hardenedsufficiently, and the mold can be pulled off and used again on the nextpart to be protected. The mold can also be left on the part to beprotected for increased protection. In such a case, where the mold actsshell on the object to be protected, the use of a separating medium onthe mold can be omitted.

The broken lines shown in FIG. 9 indicate two possible weak spots 30provided on the periphery. These weak spots 30 divide the sleeve 32 intohalves 34, 36.

By the arrangement according to FIG. 10, it is possible to separate thetwo center strips 38. This facilitates the removal of the remaininghalves 40, 42 or of an enclosed protective device.

The broken lines in FIG. 11 signify two continuous weak spots.

FIG. 12 shows a weak spot which is formed by strips of material 44, 46.The cross-sectional area over the strip (arrow) may be severed, forexample, by cutting it with a knife from the outside or by pulling awire inserted between the strips. The halves 34, 36 can then be removed.The illustration in FIG. 12 also shows a groove 48.

FIG. 13 shows a weak spot which is formed by the strip 50. Because ofits profile, the strip 50 has a dovetailed shape. This area ofseparation guarantees that even after the destruction of thecross-sectional area above the strip, the halves 34, 36 remain next tothe threads until they can be pulled off.

FIG. 14 shows a weak spot that is formed by the strips 52, 54. Thestrips 52, 54 also have a "dovetail profile" and the same purpose asexplained in the description pertaining to FIG. 13.

FIG. 15 shows a longitudinal, cross-sectional view of a sleeve. A wire56 is inserted in the protective device. One end of the wire 56 includesan ear 58, and the other end includes an anchor 60. The anchor 60 isembedded away from the cutting surface into one of the halves 34, 36. Inaddition, a recess 62 is shown over the ear 58.

FIG. 16, like FIG. 15, shows a longitudinal cross-sectional view of asleeve. However, a wire 56' is bent into loops.

Reference is made now to FIGS. 17-23. A protective device 73 for threadsconsists of a steel sleeve 74 with a lining 75 of elastomeric material.The protective device 73 is screwed onto the end of a pipe 71 having anouter thread 72. On the front side of the steel sleeve there are pivots76. A tool can attach onto the pivots in order to transfer torque to thesleeve and screw it onto the pipe. A cylindrical closing stopper 77 hasan inner end with a bottom 78. The closing stopper slides into the pipe71.

The outer periphery of the closing stopper 77 is provided with sealinglips 79. When pressing the closing stopper into the pipe 71, the sealinglips are bent over to the extent required by the diameter of the pipe.Thus, different sizes of pipe diameters may be blocked with the sameclosing stopper. Simultaneously, the frictional force to be overcomeduring the pressing in of the stopper is kept low. Hermetic sealingagainst the penetration of such elements as moisture, aggressive gases,and dust can be achieved by the arrangement of several lips as shown inFIGS. 17 to 19.

According to other aspects of the present invention shown in FIGS. 20and 21, the closing stopper has a collar 85 or a collar 86. Thesecollars surround the pipe ends and thereby protect the outside threadsor welding chamfers 87.

In order to protect the inside threads on pipe ends, one mayalternatively use a steel sleeve 80. The steel sleeve 80 presses anelastomeric material 81 into the individual thread turns (FIG. 22).

The inner, open end of the steel sleeve 80 is closed by a disk-shapedstopper 82 (FIGS. 22 and 23). The end of the stopper that would normallypoint inward toward the pipe includes a projection 83 that narrowsconically in the direction of the pipe. The end of the closing stopperthat points outward, away from the pipe, is also made with a conicalprojection 84 that is capable of yielding when the closing stopper ispressed into the sleeve 80. Thus, the entire inside cross-sectional areaof the sleeve is sealed.

The projection 83 points inward and attaches onto the end of the sleeve80, behind the innermost edge. Thus, it keeps the closing stopper frombeing pulled out.

In the lower half of FIG. 22, the sleeve 80 is shown with a collar 85that reaches radially inward into the interspace between the projections83, 84. Thus, the sealing effect is enhanced. The conical slanting ofthe projections facilitates pressing the stopper into the steel sleeveof the protective device. By means of these simple embodiments, thepipes can be exposed to weather for a long period without the danger ofa corrosion of either the threads or interiors of the pipes.

What is claimed is:
 1. A method of manufacturing a protective device forthreads on an end of a pipe, said threads defining a corrugated surface,comprising:mounting a mold around said threads to provide a cavitybetween said threads and said mold, said cavity being unfilled;inserting an elongate tear element into said cavity between said moldand said threads; and filling said cavity with polyurethane by injectingsaid polyurethane into said cavity under pressure to form a protectivecovering for said threads and forming a tear-open lug on said protectivecovering, said protective covering engaging said threads and beingsubstantially adjacent said corrugated surface of said threads.
 2. Amethod of manufacturing a protective device for threads on an end of apipe, said threads defining a corrugated surface, comprising:mounting amold around said threads to provide a cavity between said threads andsaid mold, said cavity being unfilled; inserting an elongate tearelement into said cavity between said mold and said threads; and fillingsaid cavity with polyurethane by injecting said polyurethane into saidcavity under pressure to form a protective covering for said threadssaid mold forming a predetermined breaking line in said protectivecovering, said protective covering engaging said threads and beingsubstantially adjacent said corrugated surface of said threads.
 3. Amethod of manufacturing a protective device for threads on an end of apipe, said threads defining a corrugated surface, comprising:mounting amold around said threads to provide a cavity between said threads andsaid mold, said cavity being unfilled; filling said cavity with aprotective material to form a protective covering for said threads andforming a tear-open lug on said protective covering, said protectivecovering engaging said threads and being substantially adjacent saidcorrugated surface of said threads.
 4. A method of manufacturing aprotective device as claimed in claim 3 wherein said protective materialis injected into said cavity under pressure.
 5. A method ofmanufacturing a protective device as claimed in claim 4, wherein saidcavity between said mold and said threads is filled with elastomericmaterial.
 6. A method of manufacturing a protective device as claimed inclaim 5 wherein said cavity is filled with polyurethane.
 7. A method ofmanufacturing a protective device for threads on an end of a pipe, saidthreads defining a corrugated surface, comprising:mounting a mold aroundsaid threads to provide a cavity between said threads and said mold,said cavity being unfilled; filling said cavity with a protectivematerial to form a protective covering for said threads said moldforming a predetermined breaking line in said protective covering, saidprotective covering engaging said threads and being substantiallyadjacent said corrugated surface of said threads.
 8. A method ofmanufacturing a protective device as claimed in claim 7 wherein saidprotective material is injected into said cavity under pressure.
 9. Amethod of manufacturing a protective device as claimed in claim 8wherein said cavity between said mold and said threads is filled withelastomeric material.
 10. A method of manufacturing a protective deviceas claimed in claim 9 wherein said cavity is filled with polyurethane.